The present invention relates to a multi-usable heat transfer ink ribbon used in a heat transfer type hard copy printer. More particularly, the invention relates to a heat transfer ink ribbon wherein the same portion of the ink layer can be used repeatedly for printing.
Multi-usable heat transfer ink ribbons of this type which have been proposed heretofore include an ink ribbon wherein a nontransferable sponge-like resinous layer is impregnated with a heat transfer ink, an ink ribbon wherein a pigment having strong cohesive force is dispersed in a heat transfer ink to form a barrier like a stone wall against the migration of the ink by agglomeration of the pigment and the ink is flowed out in increments through the barrier, and an ink ribbon wherein porous particles are bonded to each other with a binder to form a porous layer and a heat transfer ink contained in the pores of the porous particles and the voids between the particles is flowed out in increments.
However, all proposals mentioned above have a drawback that since large amounts of the nontransferable materials must be present in the ink layer, the ink layer inevitably becomes thicker as compared with the amount of the transfer ink, which results in formation of unclear printed images. Further, they have another drawback that some portion of the heat transfer ink contained in the ink layer is not flowed out due to capillary action and remains unused in the ink layer.
In other words, the amount of the heat transfer ink which can be effectively used for printing is small as compared to the thickness of the layer containing the heat transfer ink which has a strong dependence with the clearness of printed images, so that clear printed images cannot be obtained at every repeated use. Further, the materials which must not be transferred are transferred by accident, which results in formation of printed images having unevenness in their optical density and formation of incomplete printed images involving defects such as voids and dropout portions at repeated use.
It is an object of the present invention to provide a multi-usable heat transfer ink ribbon which can be used repeatedly many times, though the whole of the ink layer is transferable by incorporating into the ink layer no nontransferable material which hinders the transfer of the ink.
This and other objects of the invention will become apparent from the description hereinafter.